Background/Discussion/Critique

The sentinel lymph node (SLN) is the "first lymph node in a nodal basin to drain the primary tumor." In theory, a malignancy spreads to axillary lymph nodes (ALN's) and progresses in an orderly fashion from the primary tumor to the SLN and subsequently to the other ALN's. If the SLN is not involved, then other ALN's should have a very low likelihood to be affected by metastases. For the most part this has held true. In reported series, there has been a 2 procedures. The incidence of arm lymphedema and other long term complications can be as high as 5 in patients with, for the most part, T1 sions) had SLN positive rate of 48.9%. For tumors over 5 cm (T3 lesions), the SLN positive rate was 66.7%. The rate of spread to other ALN's beyond the SLN was 46.7% of those 60 patients that had the SLN positive. Age, histologic type, nuclear grade, presence of lymphovascular invasion, mitotic count and progesterone receptor status were evaluated and found not to have a significant relationship with ALN metastases beyond the SLN. Increased incidence of ALN metastases beyond the SLN was significantly associated with tumor size greater than 2 cm and disease in the SLN larger than 2 mm (macrometastases). Estrogen receptor negativity also predicted for an increased incidence of other ALN metastases when evaluating this factor alone (univariate analysis). However, when taking into consideration other prognostic factors, estrogen receptor status lost its significance. The following table organizes the rate of non-SLN ALN metastases in relation to size of the primary tumor and SLN metastases.

Primary Tumor Size

SLN Metastases Size

Non-SLN ALN Metastases Rate

2 cm or less

2 mm or less

0% (0/18)

2 cm or less

over 2 mm

50% (9/18)

over 2 cm

2 mm or less

66.7% (6/9)

over 2 cm

over 2 mm

86.7% (13/15)

The authors' conclusions are that patients having a primary tumor of 2 cm or less and only micrometastases (2 mm or less) in the SLN are at a very low (0%) risk of metastases beyond the SLN. Thus, the surgeon may forego the ALN dissection of levels I and II.

Based on this report, the valuse of SLN biopsies remain an open question. The number of patients evaluated here were low (only 18 patients fit into the above specified very low risk category), hence the 95% confidence interval was shown to be from 0 , no explanation for the reason that 40 patients were not taken to completion ALN dissection was provided. Perhaps, those in the 40 with positive SLN's may have added more information or at the very least improved the confidence interval. The false negative rate was on the order nearly 3% for those that received a completion dissection of the ALN's. The additional information from the other 40 patients may have helped clarify that result (although most current series are in the same range of that 3%).

Extensive information on the false negative patients was not reported. Information on factors that may influence the rate of false negative SLN biopsies could probably help increase surgeons' suspicion in future high risk cases so that ALN metastases are not missed.

The ALN dissection has been shown to be prognostic, diagnostic and even therapeutic in some series. This has always been a contention of using SLN biopsy in place of a complete level I and II ALN dissection. However it is difficult to argue with an accuracy rate of 5% or less in most current series the utility of an ALN dissection in a patient who is SLN negative. A positive SLN biopsy remains a different story as indicated above. Finally, a learning curve is associated with this procedure. Guilliano, one of the pioneers of SLN biopsy, admitted that his rate of finding the SLN in his first 60 patients was 65%. The 90+% ability of locating the SLN in most current series is a testament to the improvement in technique or the lack of reporting of their initial experience.

SLN biopsies alone for negative biopsies may soon become the standard of care. However it is still very controversial whether oncologists lose valuable prognostic and diagnostic information and even therapeutic benefit with complete elimination of the ALN dissection in patients with a positive SLN biopsy (micro- or macroscopic). The American College of Surgeons Oncology Group is currently running a trial of SLN biopsy patients randomized to completion ALN dissection versus no further ALN surgery. Hopefully, this will provide some definitive answers.